Alignment of BAp Crystallites in Cortical Bone of Human Mandible

Objectives: In recent years, bone quality has garnered attention in addition to bone mineral density (BMD) as a parameter for evaluating bone strength. In particular, the alignment of biological apatite (BAp) crystallites responds to local stress, and assessment of BAp crystalline orientation can therefore be used to identify the direction and regions subjected to mechanical stress. BAp crystalline orientation was assessed in the cortical bone of the human dentulous mandible and the posterior of human edentulous mandible. BAp crystalline orientation has not yet been assessed on the anterior cortical bone of the human edentulous mandible. Therefore, we assessed BMD and BAp crystalline orientation, and investigated the relationship between these two parameters, in connection with the extent of alveolar bone resorption in the anterior area of human edentulous mandible.
Methods: Japanese edentulous mandibles were classified by the extent of alveolar bone resorption. BAp crystalline orientation and BMD were measured in the alveolar area and base of the mandible of the site corresponding to the central incisor.
Results: BAp crystalline orientation was oriented in the direction of masticatory force orientation in the area with less alveolar bone resorption. However, BAp crystalline orientation was not observed in the area with bone resorption. BAp crystalline orientation in the base of the mandible did not show uniaxial preferential alignment in all classifications. BMD was not affected by the degree of bone resorption.
Conclusions: These findings demonstrated that in the anterior cortical bone of the human edentulous mandible, BAp crystalline orientation of the alveolar areas varies with morphological changes of the bone.